3-D Characterization of Urban Areas Using High-Resolution Polarimetric SAR Tomographic Techniques and a Minimal Number of Acquisitions

Abstract

This article addresses the 3-D reconstruction of urban areas using a minimal number of Synthetic Aperture Radar (SAR) acquisitions, that is, a set of three images, characterized by intermediate spatial resolution features. In such extreme conditions, conventional tomographic techniques reveal unadapted to refined 3-D imaging purposes, either due to the resulting intrinsic coarse vertical resolution, or to the low dimensionality of the data set, that prevents any separation of complex mixed scattering patterns. A new high-resolution (HR) tomographic estimator, based on a polarimetric signal subspace fitting criterion, is proposed to overcome these limitations, as this method adapts to the statistical behavior of the backscattered signals using robust metrics. The optimization of the corresponding focusing criterion is led through a new polarimetric alternating projection algorithm, characterized by a low computational cost, which may also be used to optimize the polarimetric the deterministic maximum likelihood criterion. The proposed polarimetric signal subspace fitting technique is shown to outperform the other studied HR techniques over both simulated signals and data acquired by the DLR's ESAR sensor at L-band over Dresden city, Germany. Finally full-rank polarimetric tomographic estimators are proposed that generalize nonparametric polarimetric estimators, and permit to estimate second-order polarimetric representations in 3-D, instead of unitary rank target vector with their conventional versions. This approach makes it possible to characterize polarimetric scattering mechanisms in 3-D.

SAR Features and Techniques for Urban Planning—A Review

“…Concluding this section, it is essential to recognize that new methods with various characteristics appear constantly, giving rise to very detailed representations of tomographic urban representations [136][137][138]. Accordingly, Rambour et al proposed [136] a method for urban surface reconstruction in SAR tomography by graph cuts.…”

Forest Height Estimation Using a Single-Pass Airborne L-Band Polarimetric and Interferometric SAR System and Tomographic Techniques

“…Such an acquisition is equivalent to using a three-element equi-spaced array, with an inter-element spacing equal to B/2, as shown in Figure 3. The resulting dual-baseline interferometric and polarimetric SAR system may be used to reconstruct the scene 3D reflectivity, as shown in [17] for urban areas. Compared to a classical repeat-pass acquisition system, the dual-baseline TomoSAR configuration used here presents several advantages.…”

“…Compared to single polarization tomography, the use of several polarization channels results in an undeniable increase of performance improvement for recovering the physical features of the observed medium. Polarimetric diversity also provides a better estimation accuracy for polarimetric tomographic estimators than single polarization ones, as shown in [17,19]. Various polarimetric tomographic techniques are listed in [17] where their performance is compared in details.…”

“…Polarimetric diversity also provides a better estimation accuracy for polarimetric tomographic estimators than single polarization ones, as shown in [17,19]. Various polarimetric tomographic techniques are listed in [17] where their performance is compared in details.…”

“…Under these assumptions, HR techniques may hence be used to estimate the ground elevation as well as the phase center of the canopy, as two well localized contributions. Most HR polarimetric tomographic estimators are multi-dimensional approaches, which provide precise estimates of elevation and polarimetric parameters, even for coherent scatterers, as demonstrated in [17]. Nevertheless, multi-dimensional approaches usually suffer from a high computational complexity, and, to perform tomographic processing over a large forested area, a mono-dimensional HR approach is computationally attractive.…”